1. Field of the Invention
The present invention generally relates to optical disk units, and more particularly to an optical disk unit which uses a writable (recordable) or rewritable optical disk.
2. Description of the Related Art
Generally, in an optical disk called a compact disk (CD), a spiral track is formed at a constant liner density from an inner periphery to an outer periphery of the disk. In addition, information can be recorded in a CD called a CD-Recordable (CD-R). When recording the information on the CD-R, the information is also recorded at a constant linear density on a spiral track which is formed from the inner periphery to the outer periphery of the CD-R. Information is similarly recorded on a CD called a CD-Rewritable (CD-RW), that is, at a constant linear density on a spiral track which is formed from the inner periphery to the outer periphery of the CD-RW. The information is rewritable in the case of the CD-RW.
Recording and reproducing systems used to record information on and reproduce information from the optical disks such as the CD-R and the CD-RW can generally by categorized into a constant linear velocity (CLV) system and a constant angular velocity (CAV) system. There is also a recording and reproducing system called a zone constant linear velocity (ZCLV) system which is a modification of the CLV system. For example, such recording and reproducing systems are proposed in Japanese Laid-Open Patent Applications No. 11-296858, 2000-11384, No. 2000-48484, No. 7-21585, No. 9-231580, No. 9-270129, No. 10-79124, and No. 11-66726.
According to the CLV system, the optical disk is rotated at a constant linear velocity. Hence, although data management and rotational velocity control become slightly complex, it is possible to maximize a recording capacity by the CLV system. On the other hand, according to the CAV system, the optical disk is rotated at a constant angular velocity, that is, at a constant number of revolutions. For this reason, the data management and the rotational velocity control become simple, but the recording capacity is slightly sacrificed according to the CAV system. According to the ZCLV system, a recording surface of the optical disk is divided into a plurality of zones, and the linear velocity is maintained constant within each of the zones, similarly to the CLV system. The ZCLV system changes the rotational velocity for each zone so that the rotational velocity increases towards the outer periphery of the optical disk.
When recording information on the recordable or rewritable optical disks such as the CD-R and the CD-RW, the CAV system or the ZCLV system is employed by placing priority on the ease of the rotation control of the optical disk. Particularly, the CAV system is desirable in order to satisfy the recent demands to improve the recording velocity (rate) and realize a recording such as a 20-times speed recording.
However, when the optical disk in conformance with the CLV system, such as the CD-R and the CD-RW, is rotated according to the CAV system, the linear velocity increases as a radial position on the optical disk moves towards the outer periphery of the optical disk. But since an optimum recording laser power increases proportionally to the linear velocity, it is not possible to record the information at an optimum recording power in an outer peripheral portion of the optical disk if the recording power is maintained constant.
In addition, a setting of a write strategy (light emission waveform of a semiconductor laser) shown in FIG. 1 with respect to the CD-R does not lead to an ideal recording mark on the optical disk as shown in FIG. 2A when a high-speed write is carried out. Instead, the actual recording mark on the optical disk typically becomes as shown in FIG. 2B when the high-speed write is carried out. In FIG. 2B, a portion {circle around (1)} corresponds to a shape which is formed due to insufficient heat transfer to the optical disk immediately after the irradiation of the laser beam on the optical disk starts, and a portion {circle around (2)} corresponds to a shape which is formed due to insufficient heat release immediately after the irradiation of the laser beam on the optical disk ends.
Accordingly, as shown in FIG. 1, with respect to a recording clock period T at each linear velocity, the laser power at a leading portion of a recording pulse is set larger than at a trailing portion of the recording pulse, in a form of an extra pulse, and a recording pulse width is set narrower than the actual width which is to be written. With regard to the recording clock period T, 1T denotes a 1 times-speed reproduction of 1.2 to 1.4 m/s, for example, and amounts to 231.4 ns. Such a modification of the write strategy is mainly made by changing a value xcex81 which prescribes the recording pulse width nxe2x88x92xcex81T indicated by {circle around (1)} in FIG. 1, and/or changing a power xcex94P of the extra pulse indicated by {circle around (4)} in FIG. 1, where n denotes an integer from 2 to 11 of an EFM signal. In FIG. 1, a portion {circle around (2)} corresponds to a pulse width xcex1T, and a portion {circle around (3)} corresponds to a recording power Pw. 
In addition, FIG. 3 shows a write strategy with respect to the CD-RW using multi-recording pulses. In the case of the recent high-speed write with respect to the optical disk, a peak pulse width at a leading portion of the multi-recording pulses is set wide with respect to the recording clock period T for each linear velocity, so as to facilitate heat transfer to the optical disk immediately after the irradiation of the laser beam on the optical disk starts. Moreover, an OFF-pulse width at a last portion of the multi-recording pulses is set narrow so as to adjust the remaining heat effect. In order to form an ideal recording mark on the optical disk, such a modification of the write strategy is mainly made by changing a peak pulse width xcex82 at a portion {circle around (1)} shown in FIG. 3, and/or changing an OFF-pulse width xn at a portion {circle around (2)} shown in FIG. 3. In FIG. 3, a portion {circle around (3)} corresponds to an intermediate pulse width.
In any case, the setting of the write strategy is changed for each recording linear velocity. For this reason, in the case of the CD-R, there is a problem in that the recording cannot be made under an optimum recording condition if the value xcex81 which prescribes the recording pulse width nxe2x88x92xcex81T and the power xcex94P of the extra pulse remain constant. In the case of the CD-RW, there is a problem in that the recording cannot be made under an optimum recording condition if the peak pulse width xcex82 and the OFF-pulse width xn remain constant.
Such problems similarly occur when rotating the optical disk, such as the CD-R and the CD-RW, according to the ZCLV system.
Accordingly, it is a general object of the present invention to provide a novel and useful optical disk unit in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide an optical disk unit which can always record information with respect to a recordable or rewritable optical disk at an optimum recording condition, using the CAV system or the ZCLV system which can improve the recording velocity as compared to the CLV system.
Still another object of the present invention is to provide an optical disk unit which can cope with a case where an optical disk used has a low recording sensitivity and/or a case where a light source used has a low maximum power output.
A further object of the present invention is to provide an optical disk unit which can cope with a case where optical disks used are manufactured by different manufacturers.
Another object of the present invention is to provide an optical disk unit which can cope with a case where optical disks used are manufactured by the same manufacturer but are of different types.
Still another object of the present invention is to provide an optical disk unit comprising a light source irradiating a light beam on a recordable optical disk; rotationally driving means for rotating the optical disk; setting means for presetting a value xcex81 which prescribes an optimum recording pulse width of the light source for a case where the optical disk is rotated at a predetermined linear velocity on a track located at a predetermined radial position on the optical disk, and an optimum power ratio xcex94P of an extra pulse at a leading portion of the recording pulse where power is increased; test write means for carrying out a test write a predetermined number of times prior to recording, on the track located at the predetermined radial position on the optical disk, by driving the light source at a recording power which differs for each step, while rotating the optical disk by the rotationally driving means at the predetermined linear velocity, using the value xcex81 which prescribes the optimum recording pulse width the optimum power ratio xcex94P of the extra pulse which are preset by the setting means; reference optimum recording power determination means for reproducing data recorded by the test write carried out by the test write means, and determining an optimum recording power Pwo based on characteristic values of the reproduced data; recording rotation control means for rotating the optical disk by the rotationally driving means at a predetermined number of revolutions when recording information; light emission waveform updating computation means for successively calculating a value xcex81(v) which prescribes the recording pulse width, a power ratio xcex94P(v) and an optimum recording power Pwo(v), depending on an arbitrary linear velocity v at a recording target track which is to be recorded, by adding corrections dependent on the arbitrary linear velocity v with respect to the value xcex81 which prescribes the optimum recording pulse width when recording the information, the power ratio xcex94P and the optimum recording power Pwo which is determined by the reference optimum recording power determination means; and recording light source control means for recording the information while controlling a light emission waveform of the light source based on the value xcex81(v) which prescribes the recording pulse width, the power ratio xcex94P(v) and the optimum recording power Pwo(v) which are successively calculated by the light emission waveform update computation means. According to the optical disk unit of the present invention, it is possible to improve the recording velocity because the optical disk is basically rotated at the predetermined number of revolutions in conformance with the CAV system during the recording. Furthermore, since the value xcex81(v) which prescribes the recording pulse width, the power ratio xcex94P(v) and the optimum recording power Pwo(v) are successively calculated, and the recording is carried out while controlling the light emission waveform of the light source based on the calculated values, it is possible to always record the information under a stable recording condition in conformance with the CAV system, even if the linear velocity during the recording changes.
The optical disk unit may further comprise judging means for judging whether or not the optimum recording power Pwo(v) calculated by the light emission waveform update computation means depending on the arbitrary linear velocity v on the track reaches a predetermined upper limit value of an output power of the light source, where the recording rotation control means switches rotation to rotate the optical disk by the rotationally driving means at a constant linear velocity in a track region in which the judging means judges that the optimum recording power Pwo(v) reaches the predetermined upper limit value of the output power of the light source. According to the optical disk unit of the present invention, a decision is made to determine whether or not the optimum recording power Pwo(v) reaches the maximum output Pwmax of the light source. The recording is carried out in conformance with the CAV system at the original predetermined number of revolutions in a track region in which the maximum output Pwmax is not exceeded. On the other hand, in a track region in which the maximum output Pwmax is reached or exceeded, the recording is carried out in conformance with the CLV system at the constant linear velocity which introduces no change in the linear velocity v. For this reason, it is possible to continue the recording at the maximum output of the light source, and it is thus possible to cope with cases where the light source used has a low maximum output for the recording power and the optical disk used has a low recording sensitivity, by a minimum required decrease in the recording velocity.
A further object of the present invention is to provide an optical disk unit for recording information on a recordable optical disk which has a recording surface divided into a plurality of zones in a radial direction thereof, by rotating the optical disk at a rotational velocity which is different for each zone so that a linear velocity within each zone is approximately constant, comprising a light source irradiating a light beam on the optical disk; rotationally driving means for rotating the optical disk; setting means for presetting a value xcex81 which prescribes an optimum recording pulse width of the light source for a case where the optical disk is rotated at a predetermined linear velocity on a track located at a predetermined radial position on the optical disk, and an optimum power ratio xcex94P of an extra pulse at a leading portion of the recording pulse where power is increased; test write means for carrying out a test write a predetermined number of times prior to recording, on the track located at the predetermined radial position on the optical disk, by driving the light source at a recording power which differs for each step, while rotating the optical disk by the rotationally driving means at the predetermined linear velocity, using the value xcex81 which prescribes the optimum recording pulse width the optimum power ratio xcex94P of the extra pulse which are preset by the setting means; reference optimum recording power determination means for reproducing data recorded by the test write carried out by the test write means, and determining an optimum recording power Pwo based on characteristic values of the reproduced data; recording rotation control means for rotating the optical disk by the rotationally driving means at a rotational velocity which is different for each zone so that a predetermined linear velocity is approximately obtained within each zone when recording information; light emission waveform updating computation means for successively calculating a value xcex81(v) which prescribes the recording pulse width, a power ratio xcex94P(v) and an optimum recording power Pwo(v), depending on an arbitrary linear velocity v at a recording target zone which is to be recorded, by adding corrections dependent on the arbitrary linear velocity v with respect to the value xcex81 which prescribes the optimum recording pulse width when recording the information, the power ratio xcex94P and the optimum recording power Pwo which is determined by the reference optimum recording power determination means; and recording light source control means for recording the information while controlling a light emission waveform of the light source based on the value xcex81(v) which prescribes the recording pulse width, the power ratio xcex94P(v) and the optimum recording power Pwo(v) which are successively calculated by the light emission waveform update computation means. According to the optical disk unit of the present invention, the setting of the value xcex81 which prescribes the optimum recording pulse width and the power ratio xcex94P and the determination of the optimum recording power Pwo only need to be carried out once based on a PCA which has the predetermined radial position and in which the linear velocity is the predetermined linear velocity. Thereafter, the value xcex81(v) which prescribes the recording pulse width, the power ratio xcex94P(v) and the optimum recording power Pwo(v) can be successively calculated and set depending on the linear velocity v of the target recording zone, so that it is possible to always record the information under a stable recording condition, even with respect to the ZCLV system.
The optical disk unit may further comprise judging means for judging whether or not the optimum recording power Pwo(v) calculated by the light emission waveform update computation means depending on the arbitrary linear velocity v on the track reaches a predetermined upper limit value of an output power of the light source, where the recording rotation control means switches rotation to rotate the optical disk by the rotationally driving means at a linear velocity with which the predetermined upper limit value becomes the optimum recording power Pwo(v) in a recording zone region in which the judging means judges that the optimum recording power Pwo(v) reaches the predetermined upper limit value of the output power of the light source. According to the optical disk unit of the present invention, a decision is made to determine whether or not the optimum recording power Pwo(v) reaches the maximum output Pwmax of the light source. The recording is carried out in conformance with the CLV system at the original predetermined linear velocity in a recording zone region in which the maximum output Pwmax is not exceeded. On the other hand, in a recording zone region in which the maximum output Pwmax is reached or exceeded, the recording is carried out in conformance with the ZCLV system at the constant linear velocity which introduces no change in the linear velocity v within each recording zone. For this reason, it is possible to continue the recording at the maximum output of the light source, and it is thus possible to cope with cases where the light source used has a low maximum output for the recording power and the optical disk used has a low recording sensitivity, by a minimum required decrease in the recording velocity.
The optical disk unit may further comprise manufacturer judging means for judging a manufacturer of the optical disk based on an identification code prerecorded on the optical disk, where the light emission waveform updating computation means calculates the value xcex81(v) which prescribes the recording pulse width, the power ratio xcex94P(v) and the optimum recording power Pwo(v), depending on the arbitrary linear velocity v and coefficients which are preset for each manufacturer judged by the manufacturer judging means. According to the optical disk unit of the present invention, the media manufacturer of the optical disk used is judged based on the identification code prerecorded on the optical disk, and the value xcex81(v) which prescribes the recording pulse width, the power ratio xcex94P(v) and the optimum recording power Pwo(v) are respectively calculated by taking into consideration the coefficients of the judged media manufacturer. The coefficients are preset for each of the media manufacturers. As a result, it is possible to. appropriately cope with the differences among the media manufacturers of the optical disk which is used by the optical disk unit.
Furthermore, the manufacturer judging means may further judges a type of the optical disk, and the light emission waveform updating computation means uses for the calculation values which are obtained by multiplying constants to corresponding ones of the coefficients depending on the type of the optical disk judged by the manufacturer judging means. According to the optical disk unit of the present invention, by also judging the type of the optical disk, the value xcex81(v) which prescribes the recording pulse width, the power ratio xcex94P(v) and the optimum recording power Pwo(v) are calculated by taking into consideration the values which are obtained by multiplying the coefficients which differ depending on the type of the optical disk with respect to the corresponding coefficients which are preset for each judged media manufacturer. Consequently, it is possible to appropriately cope with optical disks manufactured by different media manufacturers as well as different type of optical disks.
Another object of the present invention is to provide an optical disk unit comprising a light source irradiating a light beam on a rewritable optical disk; rotationally driving means for rotating the optical disk; setting means for presetting an optimum peak pulse width xcex82 at a leading portion of multi-recording pulses of the light source and an OFF-pulse width xn at a last portion of the multi-recording pulses for a case where the optical disk is rotated at a predetermined linear velocity on a track located at a predetermined radial position on the optical disk; test write means for carrying out a test write a predetermined number of times prior to recording, on the track located at the predetermined radial position on the optical disk, by driving the light source at a recording power which differs for each step, while rotating the optical disk by the rotationally driving means at the predetermined linear velocity, using the peak pulse width xcex82 and the OFF-pulse width xn which are preset by the setting means; reference optimum recording power determination means for reproducing data recorded by the test write carried out by the test write means, and determining an optimum recording power Pwo based on characteristic values of the reproduced data; recording rotation control means for rotating the optical disk by the rotationally driving means at a predetermined number of revolutions when recording information; light emission waveform updating computation means for successively calculating a peak pulse width xcex82(v), an OFF-pulse width xn(v) and an optimum recording power Pwo(v), depending on an arbitrary linear velocity v at a recording target track which is to be recorded, by adding corrections dependent on the arbitrary linear velocity v with respect to the peak pulse width xcex82, the OFF-pulse width xn and the optimum recording power Pwo which is determined by the reference optimum recording power determination means; and recording light source control means for recording the information while controlling a light emission waveform of the light source based on the peak pulse width xcex82(v), the OFF-pulse width xn(v) and the optimum recording power Pwo(v) which are successively calculated by the light emission waveform update computation means. According to the optical disk unit of the present invention, it is possible to improve the recording velocity because the optical disk is basically rotated at the predetermined number of revolutions in conformance with the CAV system during the recording. Furthermore, since the peak pulse width xcex82(v), the OFF-pulse width xn(v) and the optimum recording power Pwo(v) are successively calculated, and the recording is carried out while controlling the light emission waveform of the light source based on the calculated values, it is possible to always record the information under a stable recording condition in conformance with the CAV system, even if the linear velocity during the recording changes.
The optical disk unit may further comprise judging means for judging whether or not the optimum recording power Pwo(v) calculated by the light emission waveform update computation means depending on the arbitrary linear velocity v on the track reaches a predetermined upper limit value of an output power of the light source, where the recording rotation control means switches rotation to rotate the optical disk by the rotationally driving means at a constant linear velocity in a track region in which the judging means judges that the optimum recording power Pwo(v) reaches the predetermined upper limit value of the output power of the light source. According to the optical disk unit of the present invention, a decision is made to determine whether or not the optimum recording power Pwo(v) reaches the maximum output Pwmax of the light source. The recording is carried out in conformance with the CAV system at the original predetermined number of revolutions in a track region in which the maximum output Pwmax is not exceeded. On the other hand, in a track region in which the maximum output Pwmax is reached or exceeded, the recording is carried out in conformance with the CLV system at the constant linear velocity which introduces no change in the linear velocity v. For this reason, it is possible to continue the recording at the maximum output of the light source, and it is thus possible to cope with cases where the light source used has a low maximum output for the recording power and the optical disk used has a low recording sensitivity, by a minimum required decrease in the recording velocity.
Still another object of the present invention is to provide an optical disk unit for recording information on a rewritable optical disk which has a recording surface divided into a plurality of zones in a radial direction thereof, by rotating the optical disk at a rotational velocity which is different for each zone so that a linear velocity within each zone is approximately constant, comprising a light source irradiating a light beam on the optical disk; rotationally driving means for rotating the optical disk; setting means for presetting a peak pulse width xcex82 at a leading portion of multi-recording pulses of the light source and an OFF-pulse width xn at a last portion of the multi-recording pulses for a case where the optical disk is rotated at a predetermined linear velocity on a track located at a predetermined radial position on the optical disk; test write means for carrying out a test write a predetermined number of times prior to recording, on the track located at the predetermined radial position on the optical disk, by driving the light source at a recording power which differs for each step, while rotating the optical disk by the rotationally driving means at the predetermined linear velocity, using the peak pulse width xcex82 and the OFF-pulse width xn which are preset by the setting means; reference optimum recording power determination means for reproducing data recorded by the test write carried out by the test write means, and determining an optimum recording power Pwo based on characteristic values of the reproduced data; recording rotation control means for rotating the optical disk by the rotationally driving means at a rotational velocity which is different for each zone so that a predetermined linear velocity is approximately obtained within each zone when recording information; light emission waveform updating computation means for successively calculating a peak pulse width xcex82(v), an OFF-pulse width xn(v) and an optimum recording power Pwo(v), depending on an arbitrary linear velocity v at a recording target zone which is to be recorded, by adding corrections dependent on the arbitrary linear velocity v with respect to the peak pulse width xcex82, the OFF-pulse width xn and the optimum recording power Pwo which is determined by the reference optimum recording power determination means; and recording light source control means for recording the information while controlling a light emission waveform of the light source based on the peak pulse width xcex82(v), the OFF-pulse width xn(v) and the optimum recording power Pwo(v) which are successively calculated by the light emission waveform update computation means 10. The optical disk unit as claimed in claim 13, further comprising judging means for judging whether or not the optimum recording power Pwo(v) calculated by the light emission waveform update computation means depending on the arbitrary linear velocity v on the track reaches a predetermined upper limit value of an output power of the light source, where the recording rotation control means switches rotation to rotate the optical disk by the rotationally driving means at a linear velocity with which the predetermined upper limit value becomes the optimum recording power Pwo(v) in a recording zone region in which the judging means judges that the optimum recording power Pwo(v) reaches the predetermined upper limit value of the output power of the light source. According to the optical disk unit of the present invention, the setting of the peak pulse width xcex82(v) and the OFF-pulse width xn(v) and the determination of the optimum recording power Pwo only need to be carried out once based on a PCA which has the predetermined radial position and in which the linear velocity is the predetermined linear velocity. Thereafter, the peak pulse width xcex82(v), the OFF-pulse width xn(v) and the optimum recording power Pwo(v) can be successively calculated and set depending on the linear velocity v of the target recording zone, so that it is possible to always record the information under a stable recording condition, even with respect to the ZCLV system.
The optical disk unit may further comprise judging means for judging whether or not the optimum recording power Pwo(v) calculated by the light emission waveform update computation means depending on the arbitrary linear velocity v on the track reaches a predetermined upper limit value of an output power of the light source, where the recording rotation control means switches rotation to rotate the optical disk by the rotationally driving means at a linear velocity with which the predetermined upper limit value becomes the optimum recording power Pwo(v) in a recording zone region in which the judging means judges that the optimum recording power Pwo(v) reaches the predetermined upper limit value of the output power of the light source. According to the optical disk unit of the present invention, a decision is made to determine whether or not the optimum recording power Pwo(v) reaches the maximum output Pwmax of the light source. The recording is carried out in conformance with the CLV system at the original predetermined linear velocity in a recording zone region in which the maximum output Pwmax is not exceeded. On the other hand, in a recording zone region in which the maximum output Pwmax is reached or exceeded, the recording is carried out in conformance with the ZCLV system at the constant linear velocity which introduces no change in the linear velocity v within each recording zone. For this reason, it is possible to continue the recording at the maximum output of the light source, and it is thus possible to cope with cases where the light source used has a low maximum output for the recording power and the optical disk used has a low recording sensitivity, by a minimum required decrease in the recording velocity.
The optical disk unit may further comprise manufacturer judging means for judging a manufacturer of the optical disk based on an identification code prerecorded on the optical disk, where the light emission waveform updating computation means calculates the peak pulse width xcex82(v), the OFF-pulse width xn(v) and the optimum recording power Pwo(v), depending on the arbitrary linear velocity v and coefficients which are preset for each manufacturer judged by the manufacturer judging means. According to the optical disk unit of the present invention, the media manufacturer of the optical disk used is judged based on the identification code prerecorded on the optical disk, and the peak pulse width xcex82(v), the OFF-pulse width xn(v) and the optimum recording power Pwo(v) are respectively calculated by taking into consideration the coefficients of the judged media manufacturer. The coefficients are preset for each of the media manufacturers. As a result, it is possible to appropriately cope with the differences among the media manufacturers of the optical disk which is used by the optical disk unit.
Furthermore, the manufacturer judging means may further judges a type of the optical disk, and the light emission waveform updating computation means uses for the calculation values which are obtained by multiplying constants to corresponding ones of the coefficients depending on the type of the optical disk judged by the manufacturer judging means. According to the optical disk unit of the present invention, by also judging the type of the optical disk, the peak pulse width xcex82(v), the OFF-pulse width xn(v) and the optimum recording power Pwo(v) are calculated by taking into consideration the values which are obtained by multiplying the coefficients which differ depending on the type of the optical disk with respect to the corresponding coefficients which are preset for each judged media manufacturer. Consequently, it is possible to appropriately cope with optical disks manufactured by different media manufacturers as well as different type of optical disks.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.